A Sparse Array Structural Health Monitoring System Based on SH Wave

Abstract

Structural health monitoring (SHM) is becoming more and more important in modern industries. The fundamental shear horizontal (SH0) wave based inspection is very attractive since SH0 wave is the unique non-dispersive wave mode in plate-like structures. For practical SHM applications, a sparse array system based on omni-directional transducers is more promising due to the low cost and simple signal processing. In this paper, we firstly proposed a new omni-directional SH wave piezoelectric transducer (OSH-PT) consisting of twelve thickness-poled, thickness-shear PZT elements. Experimental results indicated it can generate and receive single mode SH0 wave in wideband with uniform sensitivity along all directions. Then, the number of elements composing the OSH-PT was decreased to two to improve its practicability. Its performance was investigated to be acceptable. After that, the existing four types of OSH-PTs were comprehensive compared and discussed. Finally, experiments were carried out to examine the feasibility of OSH-PT based SHM system. Results indicated the proposed SHM system can accurately locate the defect with the super resolution of 0.12λ (4mm) at varied frequencies. Besides, it can also locate multi defects based on the baseline subtraction method. The good performance of the proposed SHM system was benefited from the employed single mode non-dispersive SH0 wave. This work is expected to promote the applications of SH0 wave-based SHM.